In thermal-related engineering such as thermal energy structures and nuclear waste disposal, it is essential to well understand volume change and excess pore water pressure buildup of soils under thermal cycles. However, most existing thermo-mechanical models can merely simulate one heating–cooling cycle and fail in capturing accumulation phenomenon due to multiple thermal cycles. In this study, a two-surface elasto-plastic model considering thermal cyclic behavior is proposed. This model is based on the bounding surface plasticity and progressive plasticity by introducing two yield surfaces and two loading yield limits. A dependency law is proposed by linking two loading yield limits with a thermal accumulation parameter n_c, allowing the thermal cyclic behavior to be taken into account. Parameter n_c controls the evolution rate of the inner loading yield limit approaching the loading yield limit following a thermal loading path. By extending the thermo-hydro-mechanical equations into the elastic–plastic state, the excess pore water pressure buildup of soil due to thermal cycles is also accounted. Then, thermal cycle tests on four fine-grained soils (natural Boom clay, Geneva clay, Bonny silt, and reconstituted Pontida clay) under different OCRs and stresses are simulated and compared. The results show that the proposed model can well describe both strain accumulation phenomenon and excess pore water pressure buildup of fine-grained soils under the effect of thermal cycles.

中文翻译：

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考虑热循环行为的两面热力学塑性模型

在热能工程和核废料处理等与热有关的工程中，必须充分了解热循环下土壤的体积变化和土壤孔隙水压力过大。但是，大多数现有的热力学模型只能模拟一个加热-冷却循环，并且由于多个热循环而无法捕获累积现象。在这项研究中，提出了一种考虑热循环行为的两面弹塑性模型。通过引入两个屈服面和两个载荷屈服极限，该模型基于边界表面可塑性和渐进可塑性。通过将两个负荷屈服极限与一个蓄热参数n _c链接起来，提出了一个依赖定律。，允许考虑热循环行为。参数n _c控制沿着热加载路径接近加载屈服极限的内部加载屈服极限的演变速率。通过将热-水-力学方程式扩展到弹塑性状态，还可以考虑由于热循环而造成的土壤孔隙水压力过大。然后，模拟并比较了在四种OCR和应力下对四种细粒土壤（天然Boom粘土，Geneva粘土，Bonny粉砂和再生的Pontida粘土）进行的热循环测试。结果表明，该模型可以很好地描述热循环作用下细粒土的应变累积现象和超孔隙水压力的建立。